title: Multiple contributory factors to the age distribution of disease cases: a modeling study in the context of influenza A(H3N2v).
abstract: BACKGROUND
  In late 2011 and early 2012, 13 cases of human influenza resulted from infection with a novel triple reassortant swine-origin influenza virus, influenza A (H3N2) variant. This variant was notable for its inclusion of the matrix gene from the 2009 influenza A(H1N1) pandemic virus. While most of these confirmed cases were among children, the transmission potential and likely age-dependent susceptibility to the virus was unknown. Preliminary serologic studies indicated that very young children have less protection than older children and adults.
  
  
  METHODS
  We construct a mathematical transmission model of influenza transmission that allows for external zoonotic exposure to infection and show how exposure and susceptibility-related factors contribute to the observed case distribution.
  
  
  CONCLUSIONS
  Age-dependent susceptibility to infection strongly influences epidemic dynamics. The result is that the risk of an outbreak in a highly susceptible age group may be substantially higher than in an older age group with less susceptibility, but exposure-related factors must also be accounted for when interpreting case data.
authors.affiliation: Modeling Unit, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd. NE, Atlanta, GA 30333, USA. vij4@cdc.gov
authors.forename: Manoj
authors.initials: M
authors.lastname: Gambhir
authors.forename: David L
authors.initials: DL
authors.lastname: Swerdlow
authors.forename: Lyn
authors.initials: L
authors.lastname: Finelli
authors.forename: Maria D
authors.initials: MD
authors.lastname: Van Kerkhove
authors.forename: Matthew
authors.initials: M
authors.lastname: Biggerstaff
authors.forename: Simon
authors.initials: S
authors.lastname: Cauchemez
authors.forename: Neil M
authors.initials: NM
authors.lastname: Ferguson
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D008875:Middle Aged; D008962:Models, Theoretical; D009976:Orthomyxoviridae Infections / Q000635:transmission / Q000662:veterinary / Q000821:virology; D013552:Swine; D013553:Swine Diseases / Q000635:transmission / Q000821:virology; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: emerging infection; modeling; novel influenza; zoonosis